598 
MAXGAXE«:e deposits of INDIA: ECO?fOMICS. [PaET III ; 
the available oxygen in terms of MnOo, the amount of available oxygen 
being in fact equivalent to 2 X 62-57% of Mn02. On the assumption 
of R being entirely Ba, so that the formula would be Ba.^lnO^, 
the Mn02 works out at 2r23%, but the available oxygen is equivalent 
to 2x2r23= 42*i6% Mn02. Hence it will be more convenient to 
state the available oxygen as such in the way given below : — 
Table 90. 
Available oxygen and manganese peroxide present in pyrolusite. psilo- 
melam, and hollandite. 
Formula. 
P}^ oliisite. 
Psilomelane (and hollandite). 
>In02. 
Ba2Mn05 :Mn2Mn05. 
H4Mn05. 
Available oxygen 
Mn02 equivalent of avail- 
able oxygen 
Mn02 present 
18-39 
100-00 
100-00 
7-81 1306 
42-46 77-33 
21-23 77 33 
2301 
1-2.5-14 
'V2-57 
From this it wiU be seen that in theoretically pure psUomelanes the 
amount of available oxygen should range between the limits of 7 -81 and 
23-01. Since in most psilomelanes the bulk of the R group is manganese, 
the majority of psUomelanes should range round 13% in their available 
oxvgen, this corresponding to about 77% of Mn02. Allowing for the 
fact that most psilomelanes contain a little mechanically-included im- 
purity these figures would be in actual practice a little less than 13 and 
77, respectively. The 5 analyses of psilomelane given in Chapter TV show 
70-78 to 83-13*^0 Mn02, whilst the 12 calculated analyses show from 73-14 
to 84-12% Mn02. The four analyses of hollandite, to which the foregoing 
figures as to composition also apply, show 65'63 to 75'05°o Mn02. 
As is shown below the other ores of manganese contain much smaller 
amounts of MnO., : 
% Mn02- 
-Manganite .......... 49-44 
Braunite 4311 
Hausmannite .......... 37-99 
Rhodochro -ite .......... Nil. 
The standard ore for chemical purposes is that containing 70% Mn02 
equivalent to 44-25°o manganese, and below this limit there is not much 
demand for ores for these purposes. Hence we see that for chemical 
